Systems and methods for placing materials into bone

ABSTRACT

A method for delivering material into bone deploys a cannula through soft tissue to establish a subcutaneous path into bone. The method deploys a cavity forming instrument through the cannula to form a cavity in cancellous bone. The method introduces a material into the cavity through the cannula, which includes the advancement of a tamping instrument through the cannula to urge material into the cavity.

RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 10/617,976, filed Jul. 11, 2003, and entitled “Systems andMethods for Placing Materials into Bone,” which is a divisional of U.S.patent application Ser. No. 09/804,107, filed Mar. 12, 2001, now U.S.Pat. No. 6,613,054, which is a divisional of application Ser. No.09/134,323, filed Aug. 14, 1998, now U.S. Pat. No. 6,241,734.

FIELD OF THE INVENTION

The invention generally relates to the treatment of bone conditions inhumans and other animals.

BACKGROUND OF THE INVENTION

Injection devices similar to a household caulking gun are used to injectbone cement into bone. A typical bone cement injection device has apistol shaped body, which supports a cartridge containing bone cement. Atrigger actuates a spring-loaded ram, which forces a volume of bonecement in a viscous condition through a suitable nozzle and into theinterior of a bone targeted for treatment. According to the teachings ofU.S. Pat. Nos. 4,969,888 and 5,108,404, a cavity can be first formed bycompacting cancellous bone inside the bone, into which the bone cementis injected. Conventional cement injection devices provide noopportunity to override the spring action and quickly terminate the flowof cement, should the cavity fill before the spring-actuated load cycleis completed. Furthermore, once the spring-actuated mechanism istriggered, conventional cement injection devices do not permit theinjection volume or inject rate to be adjusted or controlled in realtime, in reaction to cancellous bone volume and density conditionsencountered inside bone.

In a clinical procedure called vertebroplasty, bone cement is injectedat high pressure (typically, about 700 psi) into the interior of avertebral body, without the prior formation of a cavity. Because highpressure is used, there is little opportunity to quickly and accuratelyadjust cement flow in reaction to bone volume and density conditionsencountered. Momentum generated by high pressure-induced cement flowcontinues to propel cement into the targeted bone site even aftertermination of the high pressure.

As a result of the relatively high pressure that conventional proceduresrely upon, coupled with the effective lack of a short response time, thetargeted bone interior can suddenly overfill. Excess filling materialcan be forced outside the bone interior, and into adjoining tissueregions, where the presence of filling material is not required ordesired.

For these and other reasons, there is a need for new systems and methodsfor placing material into bones, with greater rate and volume control, afaster response time, and without requiring the use of high pressure.

SUMMARY OF THE INVENTION

The invention provides instruments, systems, and methods, which, in use,enable greater control over the placement of materials into bone.

One aspect of the invention provides A method that deploys a cannulathrough soft tissue to establish a subcutaneous path into bone. Themethod deploys a cavity forming instrument through the cannula to form acavity in cancellous bone. The method introduces a material into thecavity through the cannula, including advancing a tamping instrumentthrough the cannula to urge material into the cavity. The tampinginstrument urges the material into the cavity at a low deliverypressure. As used herein, a Alow delivery pressure@ is equivalent to thepressure at which liquid is expressed from 1 cc syringe by theapplication of moderate force to the syringe piston, which amounts to apressure that is no greater than about 360 psi.

The material can comprise medication or a material that sets to ahardened condition e.g., bone cement, or autograft tissue, or allografttissue, or synthetic bone substitute, or combinations thereof.

Features and advantages of the inventions are set forth in the followingDescription and Drawings, as well as in the appended Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view of a kit housing a system of functionalinstruments, which, in use, gain subcutaneous access to the inside of abone to compact cancellous bone and form a cavity for therapeuticpurposes;

FIG. 2 is an exploded perspective view of the kit shown in FIG. 1;

FIG. 3 is a perspective view of the subcutaneous access instrument groupthat forms a part of the system shown in FIG. 1;

FIG. 4A is a perspective view of the cavity forming instrument thatforms a part of the system shown in FIG. 1;

FIG. 4B is a section view of the catheter tube of the cavity forminginstrument, taken generally along line 4B-4B in FIG. 1;

FIG. 4C is an end view of an alternative embodiment of the cavityforming instrument shown in FIG. 4A, having a prebent stylet;

FIG. 5 is a perspective view of the material introducing instrumentgroup that forms a part of the system shown in FIG. 1;

FIGS. 6 and 7 are, respectively, top and side views of a human vertebralbody;

FIG. 8 is a top view of a vertebral body during insertion of a spinalneedle instrument to begin a bone access procedure;

FIGS. 9 to 11 are top views showing subsequent steps, after insertion ofthe spinal needle instrument shown in FIG. 8, of inserting a guide pininstrument into the vertebral body;

FIG. 12 is a perspective view showing a subsequent step, after insertionof the guide pin instrument shown in FIGS. 9 to 11, which deploys anobturator instrument deployed over the guide pin instrument with aid ofa handle;

FIG. 13 is a top view of the vertebral body, with the obturatorinstrument shown in FIG. 12 deployed;

FIG. 14 is a perspective view showing a subsequent step, after insertionof the obturator instrument shown in FIG. 12, which uses the handleshown in FIG. 12 to aid in the deployment of a cannula instrument overthe obturator instrument;

FIG. 15 is a top view of the vertebral body, with the cannula instrumentshown in FIG. 14 deployed;

FIG. 16 is a perspective view showing a subsequent step, after insertionof the cannula instrument shown in FIG. 14, which removes the obturatorinstrument from the cannula instrument, to leave the cannula instrumentand guide pin instrument in place;

FIG. 17 is a top view of the vertebral body, after the obturator removalstep shown in FIG. 16, leaving the cannula instrument and guide pininstrument in place;

FIG. 18 is a perspective view showing a subsequent step, after removalof the obturator instrument shown in FIG. 16, which uses the handleshown in FIG. 14 to aid in the deployment of a drill bit instrumentthrough the cannula instrument along the guide pin instrument;

FIG. 19 is a top view of the vertebral body, as the drill bit instrumentshown in FIG. 18 is deployed with aid of the handle to open a passageinto the interior volume of the vertebral body;

FIG. 20 is a perspective view showing a subsequent step, after removalof the drill bit instrument and guide pin instrument shown in FIG. 18,of deploying the cavity forming instrument into the vertebral body;

FIG. 21 is a top view of the vertebral body, as the expandable structurecarried by the cavity forming instrument shown in FIG. 20 is deployedinto the interior volume of the vertebral body;

FIG. 22 is a top view of the vertebral body, as the expandable structureshown in a collapsed condition in FIG. 21 is expanded to compactcancellous bone and form a cavity;

FIG. 23 is a top view of the vertebral body, after removal of theexpandable structure, showing the cavity formed by compacting cancellousbone;

FIG. 24 is a perspective view of the syringe of the material introducinginstrument group, shown in FIG. 5, being filled with a material selectedfor introduction into the cavity shown in FIG. 23;

FIG. 25 is a perspective view of the syringe shown in FIG. 24 beingjoined to a nozzle, which also forms a part of the material introducinginstrument group shown in FIG. 5;

FIG. 26 is a perspective view showing the syringe and attached nozzleshown in FIG. 25 being deployed through the cannula instrument inpreparation of introducing material into the cavity;

FIGS. 27 and 28 are perspective and top views, respectively, showing thesyringe and attached nozzle shown in FIG. 26 in use to inject materialinto the cannula instrument for passage into the cavity;

FIG. 29 is a top view of the vertebral body after a measured volume ofmaterial has been injected and the syringe and attached nozzle withdrawnfrom the cannula instrument;

FIG. 30 is a top view showing the deployment of a tamping instrument,which forms a part of the material introducing instrument group shown inFIG. 5, being deployed in the cannula instrument;

FIG. 31 is a top view showing advancement of the tamping instrument inthe cannula instrument to displace and distribute material from thecannula instrument into the cavity;

FIG. 32 is a top view of the vertebral body after removal of the tampinginstrument and cannula instrument, showing the cavity, now filled withthe material;

FIG. 33 is a perspective view of a reduced diameter cannula instrumentand associated reduced diameter material introducing instruments, whichembody features of the invention;

FIG. 34 is a perspective view of a cavity forming instrument having anexpandable cavity forming structure, which, in use, is deployed usingthe reduced diameter cannula instrument shown in FIG. 33, the cavityforming instrument having a sliding introducer sleeve shown in itsrearward position;

FIG. 35 is a perspective view of the cavity forming instrument shown inFIG. 34, with the introducer sleeve moved forward to overlie andcompress the expandable cavity forming structure;

FIG. 36 is a perspective view of the cavity forming structure shown inFIG. 35, with the introducer sleeve (shown partially in section) coupledto the proximal end of the cannula instrument, to guide the expandablestructure compressed within the sleeve into the reduced diameter cannulainstrument without damage; and,

FIG. 37 is a perspective view of the cavity forming structure shown inFIG. 36, after the expandable structure has been guided by theintroducer sleeve into the cannula instrument and is being advancedthrough the cannula instrument for deployment in bone.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a system 10 of functional instruments. In use,certain instruments of the system 10 are deployed in a purposeful mannerto penetrate tissue and gain subcutaneous access to the inside of abone. Inside bone, other instruments of the system 10 are deployed toform a cavity in cancellous bone, into which a material is placed fortherapeutic purposes.

In the illustrated embodiment, the system 10 is arranged as a prepackagekit 12 in three functional instrument groups 14, 16, and 18. The firstgroup 14 (which FIG. 3 shows outside the kit 12) comprises instrumentswhose purpose is to gain subcutaneous access to a bone interior. Thesecond group 16 (which FIG. 4 shows outside the kit 12) comprises aninstrument whose function is to create a cavity in cancellous bone. Thethird group 18 (which FIG. 5 shows outside the kit 12) comprisesinstruments whose function is to introduce a material into the cavity.

The kit 12 can take various forms. In the illustrated embodiment, thekit 12 comprises a sterile, wrapped assembly.

Further details of each functional instrument group 14, 16, and 18 andthe kit 12 follow.

I. The Subcutaneous Access Instrument Group

The number and type of instruments in the group 14 can vary. FIG. 3shows five representative instruments, each having a different size andfunction.

A. The Spinal Needle and Guide Pin

As FIG. 3 shows, one instrument comprises a conventional spinal needleassembly 20 and a guide pin instrument 26.

In use, the spinal needle assembly 20 establishes the initialsubcutaneous path leading to the targeted treatment site. The guide pininstrument 26 is deployed through this path, followed by progressivelylarger instruments, as will be described later.

The spinal needle assembly 20 comprises a stylet 22, which is slidablydeployed within a stylus 24. The stylus 24 typically has, for example,about an eleven gauge diameter. Other gauge diameters can be used,according to the gauge of the guide pin instrument 26 used.

In use, the guide pin instrument 26 is deployed through the subcutaneouspath established by the spinal needle assembly 20, by exchange with theneedle stylet 22. The guide pin instrument 26 serves to guide theestablishment of the main operative pathway to the targeted treatmentsite.

The remaining instruments 28, 30, and 32 in the group 14 share somecommon features, although they are intended, in use, to performdifferent functions. These instruments 28, 30, and 32 are each made of arigid, surgical grade plastic or metal material. These instruments 28,30, and 32 each comprises an elongated, cylindrical body having aproximal end 34 and a distal end 36.

B. The Obturator Instrument

The instrument 28 functions as an obturator. Its distal end 36 istapered to present a penetrating surface 38. In use, the surface 38 isintended to penetrate soft tissue in response to pushing or twistingforces applied by the physician at the proximal end 34.

The proximal end 34 of the obturator instrument 28 presents a flangedsurface 40, which tapers from a larger outer diameter to a smaller outerdiameter in the direction of the proximal end 34. The flanged surface 40includes an array of circumferentially spaced teeth 42.

An interior lumen 44 extends through the obturator instrument 28 fromthe distal end 36 to the proximal end 34. The interior lumen 44 is sizedto accommodate the guide pin instrument 26, as will be described ingreater detail later.

C. The Cannula Instrument

The instrument 30 functions as a cannula or guide sheath. The cannulainstrument 30 is somewhat larger in diameter than and not as long as theobturator instrument 28. The cannula instrument 30 includes an interiorlumen 46 that extends from its distal end 36 to its proximal end 34. Theinterior lumen 46 is sized to accept the obturator instrument 28. Thesize of the interior lumen 46 permits a physician to slide and rotatethe cannula instrument 30 relative to the obturator instrument 28, andvice versa, as will be described in greater detail later.

The distal end 36 of the cannula instrument 30 presents an end surface48. In use, the end surface 48 of the cannula instrument 30 is intendedto penetrate soft tissue surrounding the obturator instrument 28 inresponse to pushing or twisting forces applied at the proximal end 34.

The proximal end 34 carries an enlarged fitting 50. The fitting 50tapers from a larger diameter to a smaller diameter in the direction ofthe proximal end 34. Like the tapered flange 40 on the obturatorinstrument 28, the tapered fitting 50 has an array of circumferentiallyspaced teeth 52. The tapered fitting 50 of the cannula instrument 30possesses a larger maximum outer diameter than the maximum outerdiameter of the tapered flange 40 of the obturator instrument 28.

The cannula instrument 30 includes measured markings 118 along itslength (see FIG. 3). The measured markings 118 gauge the depth ofinsertion. The markings 118 can be placed, for example, at onecentimeter intervals. As FIG. 3 shows, the markings 118 can beconsecutively numbered, beginning at the distal end 36, so that thephysician can ascertain the insertion depth at a glance.

D. The Drill Bit Instrument

The instrument 32 functions as a drill bit. The drill bit instrument 32has generally the same physical dimensions as the obturator instrument28. Like the obturator instrument 28, the drill bit instrument 32 isintended, in use, to fit for sliding and rotational movement within theinterior lumen 46 of the cannula instrument 30.

The distal end 36 of the drill bit instrument 32 includes machinedcutting edges 54. In use, the cutting edges 54 are intended to penetratehard tissue in response to rotation and longitudinal load forces appliedat the proximal end 34 of the drill hit instrument 32.

The proximal end 34 presents a tapered flange 56, which is substantiallyidentical to the flange 40 on the obturator instrument 28. Like theobturator instrument 28, the tapered flange 56 changes from a largerdiameter to a smaller diameter in the direction of the proximal end 34.The tapered flange 56 of the drill bit instrument 32 also includes anarray of circumferentially spaced teeth 58. The form and orientation ofthe teeth 58 on the drill bit instrument 32 correspond to the form andorientation of the teeth 42 on the obturator instrument 28.

E. The Handle

The group includes a handle 60. The handle 60 engages the functionalinstruments 28, 30, and 32 in a removable, slip fit fashion to aid aphysician in manipulating the instruments during use.

The handle 60 is made from a molded or cast rigid plastic or metalmaterial. The handle 60 is shaped to be comfortably and securely graspedby a normal human hand. The shape and size to accommodate this functioncan, of course, vary. In the illustrated embodiment, the handle 60 iselongated along a main axis to fit comfortably across the palm of thehand.

The handle 60 includes a center post 62, which is integrally molded tothe handle 60 about its geometric center. The center post 62 extendsdownward to give the handle 60 a general T-shape.

The handle 60 includes two interior cavities or sockets 64 and 66 in thecenter post 62. The sockets guide the attachment between the handle 60and the instruments 28, 30, and 32. The first and second sockets 64 and66 are sized to present unique attachment sites for different functionalinstruments.

The first socket 64 includes an array of circumferentially spacedgrooves 68, which, in form and orientation, match the teeth 42 and 58 atthe proximal ends 34 of the obturator instrument 28 and the drill bitinstrument 32. The first socket 64 accepts the tapered flange 40 or 56of either the obturator instrument 28 or the drill bit instrument 32.The teeth 42 and 58 of either tapered flange 40 or 56 mesh in a slip-fitwith the grooves 68 of the first socket 64. The running slip-fit allowslongitudinal force to be applied to either instrument 28 or 32 throughthe handle 60. The running slip-fit also prevents relative rotationbetween either instrument 28 or 32 and the first socket 64, therebypermitting torsional or twisting forces to be applied to eitherinstrument 28 or 32 by the handle 60, with an increased mechanicaladvantage.

The second socket 66 is larger than the first socket 64 and is sized toaccept the larger tapered fitting 50 of the cannula instrument 30. Thesecond socket 66 includes an array of circumferentially spaced grooves70, which, in form and orientation, match the teeth 52 on the taperedfitting 50. The teeth 52 of the tapered fitting 50 mesh in a slip-fitwith the grooves 70 of the second socket 66. The running slip-fit allowsboth longitudinal and torsional forces to be applied to the cannulainstrument 30 through the handle 60, with increased mechanicaladvantage.

As shown in phantom lines in FIG. 3, a first passage 72 extends throughthe top of the handle 60, through the center post 62, and into the firstsocket 64. The passage 72 is generally aligned with the center of thefirst socket 64 and is sized to pass the guide pin instrument 26 (seeFIG. 12).

Likewise, as also shown in phantom lines in FIG. 3) a second passage 74extends through the top of the handle 60, through the center post 62,and into the second socket 66. The passage 74 is generally aligned withthe center of the second socket 66 and is sized to pass the eitherobturator instrument 28 or the drill bit instrument 32 (see FIG. 14).

Further details of the handle 60 can be found in co-pending U.S. patentapplication Ser. No. 09/014,229, filed Jan. 27, 1998, and entitled AASlip-Fit Handle for Hand-Held Instruments that Access Interior BodyRegions.

Further details regarding the use of the handle 60 and the associatedinstruments 26, 28, and 30 will be provided later.

II. The Cavity Forming Instrument

As FIG. 4A shows, the group 16 includes an instrument 76, which isdeployed through the cannula instrument 30 to a location inside bone(see FIG. 20). When so deployed, the instrument 76 serves to form acavity in cancellous bone.

The instrument 76 can be constructed in various ways. In the illustratedembodiment, the instrument 76 includes a flexible catheter tube 78having a proximal end 80 and a distal end 82. The proximal end 80carries a handle grip 84 to facilitate gripping and maneuvering thecatheter tube 78. The materials for the catheter tube 78 are selected tofacilitate its advancement through the cannula instrument 30. Thecatheter tube 78 can be constructed, for example, using standardflexible, medical grade plastic materials, like vinyl, nylon,polyethylenes, ionomer, polyurethane, and polyethylene tetraphthalate(PET). The catheter tube 78 can also include more rigid materials toimpart greater stiffness and thereby aid in its manipulation. More rigidmaterials that can be used for this purpose include stainless steel,nickel-titanium alloys (NitinolJ material), and other metal alloys.

The distal end 82 of the instrument 76 carries an expandable structure86. In the illustrated embodiment, the expandable structure 86 is madefrom a polyurethane or an elastomer (e.g., silicone or nylon) material.The structure 85 has been preformed to possess a desired shape byexposure to heat and pressure, e.g., through the use of conventionalthermoforming techniques. As FIG. 4B shows, the catheter body 78includes an interior lumen 88, which communicates with the interior ofthe structure 86. A fitting 90 on the proximal end 80 of the cathetertube 78 (see FIG. 4B) communicates with the lumen 88. The fitting 90couples the lumen 88 to a source 92 of fluid, e.g., sterile saline (seeFIG. 21), or a radiopaque contrast medium.

The fluid is introduced from the source 92 into the structure 86 underpositive pressure, causing the structure 86 to expand. During expansioninside bone, the material selected for the structure 86 preferablyresists deformation, so that the expanded shape inside bone essentiallycorresponds to its expanded shape outside bone, i.e., when in an openair environment. This allows the physician to select in an open airenvironment a structure 86 having an expanded shape desired to meet thetargeted therapeutic result, with the confidence that the expanded shapeinside bone will be similar in important respects. In addition to beingable to expand its volume while resisting deformation inside bone, thematerial of the structure 86 preferable withstands abrasion, tearing,and puncture when in contact with cancellous bone.

The shape of the structure 86, when expanded inside bone, is selected bythe physician, taking into account the morphology and geometry of thesite to be treated. The shape of the cancellous bone to be compressed,and the local structures that could be harmed if bone were movedinappropriately, are generally understood by medical professionals usingtextbooks of human skeletal anatomy along with their knowledge of thesite and its disease or injury. The physician is also able to select theexpanded shape inside bone based upon prior analysis of the morphologyof the targeted bone using, for example, plain film x-ray, fluroscopicx-ray, or MRI or CT scanning. The expanded shape inside bone is selectedto optimize the formation of a cavity that, e.g., when filled with asuitable material, provides support across the region of the bone beingtreated.

As one general guideline, in cases where the bone disease causingfracture (or the risk of fracture) is the loss of cancellous bone mass(as in osteoporosis), the selection of the expanded shape of thestructure 86 inside bone should take into account that from 30% to 90%of the cancellous bone volume should be compacted. Another generalguideline is the amount that the targeted fractured bone region has beendisplaced or depressed. The expansion of the structure 86 within thecancellous bone region inside a bone can elevate or push the fracturedcortical wall back to or near its anatomic position occupied beforefracture occurred.

In the illustrated embodiment (see FIG. 4A), the structure 86 possessesa preformed hour-glass or peanut shape. This shape is selected incontemplation of deploying the structure 86 in a vertebral body, as willbe described in greater detail later.

To facilitate deployment of the structure 86 through the cannulainstrument 30, the catheter tube 78 includes a second interior lumen 94.The lumen 94 extends from a second fitting 98 on the proximal end 80 ofthe catheter tube 78, through the body of the cannula tube 78, andthrough the interior of the structure 86 to the tip end 172 of thestructure 86. The lumen 94 receives a generally stiff stylet 96, whichcan be made from a molded plastic or stainless steel material. Thestylet 96 is inserted through the fitting 98 into the lumen 94, andincludes a threaded coupling 100 to secure the stylet 96 againstmovement. The presence of the stylet 96 serves to keep the structure 86in the desired distally straightened condition during passage throughthe cannula instrument 30 into the targeted tissue region. Once thestructure 86 is free of the cannula instrument 30 and inside hone, thestylet 96 can be withdrawn (shown by arrow 174 in FIG. 4A). This returnsnormal flexibility to the catheter tube 78 and facilitates manipulationof the structure 86 inside bone. With the stylet 96 withdrawn, the lumen94 can also serve as a pathway for introducing rinsing liquid or toaspirate debris from the bone.

in the illustrated embodiment, the stylet 96 is biased toward agenerally straight condition. In an alternative embodiment (see FIG.4C), a stylet 102 can have a preformed memory, to normally bend itsdistal region. The memory is overcome to straighten the stylet 102 whenconfined within the cannula instrument 30. However, as the structure 86and distal region of the preformed stylet 102 advance free of thecannula instrument 30, to pass into the targeted region, the preformedmemory bends the distal region of the stylet 102 and thereby shifts themain axis of the expandable structure 86. The prebent stylet 102,positioned within the interior of the structure 86, aids in altering theorientation of the structure 86, bringing it into better anatomicalignment with the targeted region.

Other types of instruments that can form cavities in cancellous bone andother interior body regions are described in copending U.S. patentapplication Ser. No. 09/055,805, entitled AStructures and Methods forCreating Cavities in Interior Body Regions, filed Apr. 6, 1998.

III. The Material Introducing Instrument Group

The group 18 includes instruments 104, 106, and 108 which serve toconvey and compact a selected material inside the cavity formed by thestructure 86. The material in the cavity provides a desired therapeuticresult, e.g., replacement of tissue mass, or renewed interior supportfor the bone, or the delivery of medication, or combinations thereof.Accordingly, the material to perform this function can be selected fromamong, e.g., a material that sets to a hardened condition, includingbone cement, autograft tissue, allograft tissue, synthetic bonesubstitute, as well as a medication, or combinations thereof.

In the illustrated embodiment, the group 18 comprises material injectioninstruments 104 and 106 and a material tamping instrument 108, whichdeliver material at a low delivery pressure, i.e., a pressure no greaterthan about 360 psi.

A. Low Pressure Material Injection instruments

In the illustrated embodiment, the material is injected by use of aconventional syringe 104, to which a specially designed injection nozzle106 is coupled. A manual actuated syringe with a push plunger can beused. Alternatively, a LeVeen Inflation Syringe with threaded plungercan be used, which can be actuated manually or by use of a mechanicalactuator.

In the illustrated embodiment, the syringe 104 is made from a clearplastic material. The syringe 104 includes a chamber 110, which receivesthe material to be injected. The material is expressed from the chamber100 by a manually advanced syringe piston 112 (see also FIG. 25).

The injection nozzle 106 connects by a threaded connector 114 to the endof the syringe 104 9 (see also FIG. 25). In the illustrated embodiment,the nozzle 106 is made from a generally flexible, inert plasticmaterial, such as such as polyethylene or another suitable polymer.Alternatively, the nozzle 106 can be made from a generally rigid plasticor metal material.

The injection nozzle 106 is sized to be advanced through the cannulainstrument 30 (see FIG. 26). The nozzle 106 includes measured markings116 along its length. The markings 116 can be placed, for example, atone centimeter intervals, to correspond with the markings 118 on thecannula instrument 30, so that the relative position of the nozzle 106within the cannula instrument 30 can be gauged. The markings 118 can,e.g., include a set point 176. Alignment of the set point 176 at theproximal end 34 of the cannula instrument 30, indicates that the distalend of the nozzle 106 is located in an aligned relationship with thedistal end 36 of the cannula instrument 30. In this arrangement, themarkings 118 are consecutively numbered with positive numbers proximallyof the set point 176 and with negative numbers distally of the set point176. The physician is thereby able to tell at a glance the location ofthe distal end of the nozzle 106, in terms of how far beyond or short ofthe distal end 36 of the cannula instrument 30 it is.

In use, the distal end of the nozzle 106 is located beyond the distalend 36 of the cannula instrument 30 within the cavity formed in thetargeted tissue region. As FIG. 5 shows, the distal end of the nozzle106, when made from a plastic material, can carry at least oneradiopaque marker 208, to enable remote visualization of the nozzleposition within the body. The syringe 104 ejects a predetermined volumeof material into the nozzle 106 in a low pressure stream into thecavity. As the material fills the cavity, the nozzle (still ejectingmaterial) is retracted from the cavity and into the cannula instrument30 itself. Further details of this function and result will be providedlater.

B. The Material Tamping Instrument

The group 18 also includes a material tamping instrument 108. Thetamping instrument 108 is made from generally rigid, inert plastic ormetal material. The tamping instrument 108 is also sized to be advancedinto the cannula instrument 30 (see FIG. 30). The free end 124 of thetamping instrument 108 is ribbed or contoured to facilitate gripping theinstrument 108 during use.

The tamping instrument 108 includes measured markings 122 along itslength. The markings 116 can be placed, for example, at one centimeterintervals, to correspond with the markings 118 on the cannula instrument30, so that the relative position of the tamping instrument 108 withinthe cannula instrument 30 can be gauged. Like the nozzle 106, themarkings 122 on the tamping instrument 108 includes a set point 178,which indicates when the distal end of the tamping instrument 108 alignswith the distal end 36 of the cannula instrument 30. Also like thenozzle 106, the markings 122 on the tamping instrument 108 areconsecutively numbered with positive numbers proximally of the set point178 and with negative numbers distally of the set point 176. Thephysician is thereby able to tell at a glance the location of the end ofthe tamping instrument 108, in terms of how far beyond or short of thedistal end 36 of the cannula instrument 30 it is. As FIG. 5 also shows,the end of the tamping instrument 108, when made from a plasticmaterial, can carry at least one radiopaque marker 210, so that itsposition can be visualized from outside the body.

After withdrawal of the nozzle 106 from the cannula instrument 30,residual material is left in the cannula instrument 30. The purpose ofthe tamping instrument 108 is to displace the residual material out thedistal end 36 of the cannula instrument 30 and into the cavity, tothereby fill the cavity without exerting undue pressure within the bone.The tamping instrument 108 thereby serves to clear residual materialfrom the cannula instrument 30, to assure that the desired volume ofmaterial is delivered into the cavity. The removal of residual materialfrom the cannula instrument 30 by the tamping instrument 108 alsoprevents seepage of material into surrounding tissue regions uponremoval of the cannula instrument 30. The tamping instrument 108 alsocompacts the material uniformly within the cavity, again without unduepressure. Further details of these functions and results will bediscussed later.

IV. The Kit

As FIGS. 1 and 2 show, in the illustrated embodiment, the kit 12includes an interior tray 126 made, e.g., from die cut cardboard,plastic sheet, or thermo-formed plastic material. The tray 126 includesspaced apart tabs 128, which hold the various instruments in a secureposition during sterilization and storage prior to use.

When packaged as a sterile assembly, the kit 12 includes an inner wrap130, which is peripherally sealed by heat or the like, to enclose thetray 126 from contact with the outside environment. One end of the innerwrap includes a conventional peal-away seal 132, to provide quick accessto the tray 126 at the instant of use, which preferably occurs in asterile environment, such as within an operating room.

When packaged as a sterile assembly, the kit 12 also includes an outerwrap 134, which is also peripherally sealed by heat or the like, toenclosed the inner wrap 130. One end of the outer wrap includes aconventional peal-away seal 136, to provide access to the inner wrap 130and its contents. The outer wrap 134 can be removed from the inner wrapin anticipation of imminent use, without compromising sterility of thecontents of the kit 12.

As FIG. 2 shows, each inner and outer wrap 130 and 134 includes aperipherally sealed top sheet 138 and bottom sheet 140. In theillustrated embodiment, the top sheet 138 is made of transparent plasticfilm, like polyethylene or MYLAR7 material, to allow visualidentification of the contents of the kit 12. The bottom sheet 140 ismade from a material that is permeable to ETO sterilization gas, e.g.,TYVEK7 plastic material (available from DuPont).

In the illustrated embodiment, the tray 126 presents the instrumentsgroups 14, 16, and 18 in an ordered, organized layout, which is arrangedto aid the physician in carrying out the intended procedure. Forexample, the layout of the tray 126 can present the instruments groups14, 16, and 18 in top-to-bottom order, according to sequence of intendeduse. For example, in a typical bone access procedure (as will bedemonstrated in greater detail later), the stylet 22 and stylus 24 ofthe spinal needle assembly 20 are deployed first, followed by the guidepin instrument 26, followed by the obturator instrument 28, then thecannula instrument 30, then the drill bit instrument 32, then the cavityforming instrument 76, then the syringe 104 and nozzle 106 instruments,and lastly the tamping instrument 108. Accordingly, the tray 126packages these instruments and components in a top-to-bottom order, withthe spinal needle assembly 20 topmost, the guide pin instrument 26 next,the obturator instrument 28 next, and so on, with the tamping instrument108 lowermost on the tray 126.

In this layout, the handle 60 is packaged to the side of the accessinstrument group 14. The tray 126 can include written labels (not shown)identifying the components contained in the kit 12.

The kit 12 also preferably includes in the tray 126 directions 144 forusing the contents of the kit 12 to carry out a desired procedure. Anexemplary procedure which the directions 144 can describe will beexplained later.

When packaged as a sterile assembly, the directions 144 can also includethe statement “For Single Patient Use Only” (or comparable language) toaffirmatively caution against reuse of the contents of the kit 12 whoseperformance characteristics and efficacy degrade after a single use. Thespinal needle assembly 20, the cavity forming instrument 76, and thematerial introducing instruments 104, 106, and 108 should, for thesereasons, be used but a single time and then discarded. The directions144 also preferably affirmatively instruct against resterilization of atleast these contents of kit 12, and also instructs the physician todispose of at least these contents of the kit 12 upon use in accordancewith applicable biological waste procedures.

The presence of the instrument groups 14, 16, and 18 packaged in thesterile kit 12 verifies to the physician that the contents are sterileand have not been subjected to prior use. The physician is therebyassured that the instrument groups meet established performance andsterility specifications.

It should be appreciated that the various instruments contained in thekit 12 can be packaged into several, smaller functional kits. Forexample, a first kit can package the access instrument group 14, asecond kit can package the cavity forming instrument group 16, and athird kit can package the material introduction instrument group 18.FIGS. 1 and 2 illustrate one of many different possible embodiments.

V. Illustrative Use of the System

The following describes use of the instrument groups 14, 16, and 18packaged in the kit 12 in the context of treating bones. This is becausethe instruments of the groups 14, 16, and 18 can be advantageously usedfor this purpose. Still, it should be appreciated that one or more ofthe instrument groups, used alone or in association with otherinstruments, can perform other diagnostic or therapeutic functions inother interior regions of the body.

In particular, the instrument groups 14, 26, and 18 will described withregard to the treatment of human vertebra. It should be appreciated,however, their use is not limited to human vertebrae. The instrumentgroups 14, 16, and 18 can be used in association with hand-heldinstruments in the treatment of diverse human or animal bone types.

A. The Vertebral Body

As FIGS. 6 and 7 show, a typical vertebra 146 includes a vertebral body148, which extends on the anterior (i.e., front or chest) side of thevertebra 146. The vertebral body 148 has the shape of an oval disk. Thevertebral body 148 includes an exterior formed from compact corticalbone 150. The cortical bone 150 encloses an interior volume ofreticulated cancellous, or spongy, bone 152 (also called medullary boneor trabecular bone).

The spinal cord 154 passes through the spinal canal 156 of the vertebra146. The vertebral arch 158 surrounds the spinal canal 156. The pedicles160 of the vertebral arch 158 adjoin the vertebral body 148. The spinousprocess 162 extends from the posterior of the vertebral arch 158, as dothe left and right transverse processes 164.

B. Treatment of a Vertebral Body

During a typical procedure, a patient lies on an operating table. Thepatient can lie face down on the table, or on either side, or at anoblique angle, depending upon the physician's preference.

The physician or surgical assistant removes the outer and inner wraps130 and 134 of the kit 12, exposing the tray 126 for use. The physicianacquires the spinal needle assembly 20 from the tray 126. As FIG. 8shows, the physician introduces the spinal needle assembly 20 into softtissue ST in the patient's back. Under radiologic or CT monitoring, thephysician advances the spinal needle assembly 20 through soft tissuedown to and into the targeted vertebra 146. The physician will typicallyadminister a local anesthetic, for example, lidocaine, through assembly20. In some cases, the physician may prefer other forms of anesthesia.

The physician directs the spinal needle assembly 20 to penetrate thecortical bone 150 and the cancellous bone 152 of the targeted vertebralbody 148. Preferably the depth of penetration is about 60% to 95% of thevertebral body 148.

FIG. 8 shows gaining access to cancellous bone through the side of thevertebral body 148, which is called postero-lateral access. However,access may be indicated through a pedicle 160, which is calledtranspedicular access. The type of access is based upon the objectivesof the treatment or for other reasons, based upon the preference of thephysician.

As FIG. 9 shows, after positioning the spinal needle assembly 20 incancellous bone 152, the physician holds the stylus 24 and withdraws thestylet 22. The physician acquires the guide pin instrument 26 from thetray 126. As FIG. 10 shows, while still holding the stylus 24, thephysician slides the guide pin instrument 26 through the stylus 24 andinto the cancellous bone 152. The physician now removes the stylus 24(see FIG. 11), leaving the guide pin instrument 26 deployed within thecancellous bone 152.

The physician next acquires the obturator instrument 28 and the handle60 from the tray 126. The physician slides the obturator instrument 28over the guide pin instrument 26, distal end first. The physician slidesthe guide pin instrument 26 through the first passage 72 and the firstsocket 64 of the handle 60. As FIG. 12 shows, the physician slides thehandle 60 along the guide pin instrument 26 toward the tapered flange 40of the obturator instrument 28, until achieving a running slip-fitbetween the first socket 64 and the tapered flange 40, in the mannerpreviously described. The obturator instrument 28 is now ready for use.

As FIG. 12 shows, the physician makes a small incision I in thepatient's back. The physician twists the handle 60 while applyinglongitudinal force to the handle 60. In response, the surface 38 of theobturator instrument 28 rotates and penetrates soft tissue ST throughthe incision I. The physician may also gently tap the handle 60, orotherwise apply appropriate additional longitudinal force to the handle60, to advance the obturator instrument 28 through the soft tissue alongthe guide pin instrument 26 down to the entry site (see FIG. 13). Thephysician can also tap the handle 60 with an appropriate striking toolto advance the surface 30 of the obturator instrument 28 into the sideof the vertebral body 148 to secure its position (as FIG. 13 shows).

The physician next slides the handle 60 along the guide pin instrument26 away from the obturator instrument 28 to disengage the tapered flange40 from the first socket 64. The physician then proceeds to slide thehandle 60 completely off the guide pin instrument 26.

The physician acquires the cannula instrument 30 from the tray 126. AsFIG. 14 shows, the physician slides the cannula instrument 30 over theguide pin instrument 26, distal end first, and, further, over theobturator instrument 28, until contact between the end surface 48 andsoft tissue ST. The physician now slides the guide pin instrument 26 andobturator instrument 26 through the second passage 74 and second socket66 of the handle 60. The physician slides the handle 60 toward thetapered fitting 50 of the cannula instrument 30 until a running slip-fitoccurs between the second socket 66 and the tapered fitting 50, aspreviously described. The cannula instrument 30 is now ready for use.

As FIG. 14 shows, the physician applies appropriate twisting andlongitudinal forces to the handle 60, to rotate and advance the cannulainstrument 30 through soft tissue ST along the obturator instrument 28.As FIG. 15 shows, when the end surface 48 of the cannula instrument 30contacts cortical bone, the physician can appropriately tap the handle60 with a striking tool to advance the end surface into the side of thevertebral body 148 to secure its position.

As FIG. 16 shows, the physician now withdraws the obturator instrument28, sliding it off the guide pin instrument 26. This leaves the guidepin instrument 26 and the cannula instrument 30 in place, as FIG. 17shows. The physician next slides the handle 60 along the guide pininstrument 26 away from the cannula instrument 30 to disengage thetapered fitting 50 from the second socket 66. The physician then slidesthe handle 60 completely off the guide pin instrument 26.

The physician now acquires the drill bit instrument 32 from the tray126. As FIG. 18 shows, the physician slides the drill bit instrument 32over the guide pin instrument 26, distal end first, through the cannulainstrument 30 until contact between the machined surface 54 and bonetissue occurs. As FIG. 18 also shows, the physician next leads the guidepin instrument 26 through the first passage 72 and first socket 64 ofthe handle 60. The physician slides the handle 60 along the guide pininstrument 26 toward the tapered flange 56 of the drill bit instrument32, until a running slip-fit occurs between the first socket 64 and thetapered flange 56, as previously described. The drill bit instrument 32is now ready for use.

As shown by FIG. 18, guided by X-ray (or another external visualizingsystem), the physician applies appropriate twisting and longitudinalforces to the handle 60, to rotate and advance the cutting edge 54 ofthe drill bit instrument 32 to open a passage 166 (see FIG. 19) throughthe bone tissue and completely into the cancellous bone 152. The drilledpassage 166 preferable extends no more than 95% across the vertebralbody 148.

The physician now slides the handle 60 along the guide pin instrument 26away from the drill bit instrument 32 to disengage the tapered flange 56from the first socket 64. The physician, further, slides the handle 60completely off the guide pin instrument 26.

The physician can now remove the drill bit instrument 32 and the guidepin instrument 26, leaving only the cannula instrument 30 in place. Thepassage 166 made by the drill bit instrument 32 remains. Subcutaneousaccess to the cancellous bone 152 has been accomplished.

The physician can now acquire the cavity forming instrument from thetray 126. As FIG. 20 shows, the physician can advance the expandablestructure 86 through the cannula instrument 30 and passage 166 into theinterior volume of the vertebral body 148, as FIG. 21 also shows. Thestructure 86 is in its normally collapsed and not expanded conditionduring deployment. The stylet 96 or 102 is inserted in the lumen 94 ofthe catheter tube 78 to provide added stiffness to the structure 86while being passed through the cannula instrument 30.

As shown in phantom lines in FIG. 20, the physician can, if desired,reconnect the handle 60 to the cannula instrument 30, to help stabilizethe cannula instrument 30 while deploying the structure 86. The secondpassage 74 of the handle accommodates the catheter tube 78 and thestructure 86, when collapsed.

As FIG. 21 shows, the structure 86 is oriented in the desired way in thepassage 166. As before explained, the bent stylet 102 can aid in thistask. Before, during, or after the orientation process, the stylet 96 or102 can be withdrawn (as FIG. 21 shows), to open the lumen 94 for use topass a rinsing liquid or negative aspiration pressure.

Sterile liquid is conveyed under pressure from the source 92 through thelumen 88 into the structure 86. As FIG. 22 shows, the structure 86expands inside bone. Expansion of the structure 86 compresses cancellousbone 152 in the vertebral body 148.

The compression forms an interior cavity 168 in the cancellous bone 152.As FIG. 23 shows, subsequent collapse and removal of the structure 86leaves the cavity 168 in a condition to receive a filling material.

The compaction of cancellous bone 152 can also exert interior force uponcortical bone, making it possible to elevate or push broken andcompressed bone back to or near its original prefracture, or otherdesired, condition.

Upon formation of the cavity 168, the physician acquires the syringe 104and injection nozzle 106 from the kit 12. As FIG. 24 shows, thephysician fills the syringe chamber 110 with the desired volume offilling material 170. As FIG. 25 shows, the physician attaches thenozzle 106 to the filled syringe 104. As FIG. 26 shows, the physicianinserts the nozzle 106 a selected distance beyond the distal end 36 ofthe cannula instrument 30 and into the cavity, guided by the markings116.

As shown in phantom lines in FIG. 26, the handle 60 can remain attachedto the cannula instrument 30 to provide stability, as the second passage74 of the handle accommodates the nozzle 106.

As FIG. 27 shows, the physician manually advances the piston 112 tocause the material 170 to flow through and out of the nozzle 106 andinto the cavity. As material 170 fills the cavity, the physicianwithdraws the nozzle from the cavity and into the cannula instrument 30.The cannula instrument 30 channels the material 170 flow toward thecavity 168. As FIG. 28 shows, the cement material 170 flows in a streaminto the cavity 168.

If the selected material 170 is bone cement, the cement material 170 isplaced into the syringe chamber 110 shortly after it is mixed from twomaterials (e.g., in an external mixing device), while it is in a lowviscosity, relatively free flowing liquid state, like a thin pancakebatter. In time (e.g., about two minutes after mixing), the consistencyof the cement material 170 will change to a substantially putty-likecharacter.

The physician operates the syringe 104 to expel the cement material 170from the chamber, through the nozzle 106, first into the cavity and theninto the cannula instrument 30. Typically, at the end of the syringeinjection process, material 170 should extend from the cavity and occupyabout 40% to 50% of the cannula instrument 30.

When a desired volume of cement is expelled from the syringe 104, thephysician withdraws the nozzle 106 from the cannula instrument 30, asFIG. 29 shows. The physician may first rotate the syringe 104 and nozzle106, to break loose the material 170 in the nozzle 106 from the ejectedbolus of material 170 occupying the cannula instrument 30.

The physician acquires the tamping instrument 108 from the kit 12. AsFIG. 30 shows, the physician advances the tamping instrument 108 throughthe cannula instrument 30. As phantom lines in FIG. 30 show, the handle60 can remain attached to the cannula instrument 30 to providestability, as the second passage 74 of the handle accommodates thetamping instrument 108.

The distal end of the tamping instrument 108 contacts the residualvolume of cement material 170 in the cannula instrument 30. As FIGS. 30and 31 show, advancement of the tamping instrument 108 displacesprogressively more of the residual material 170 from the cannulainstrument 30, forcing it into the cavity 168. The flow of material 170into the cavity 168, propelled by the advancement of the tampinginstrument 108 in the cannula instrument 30, serves to uniformlydistribute and compact the material 170 inside the cavity 168, withoutthe application of undue pressure.

The use of the syringe 104, nozzle 106, and the tamping instrument 108allows the physician to exert precise control when filling the cavitywith material 170. The physician can immediately adjust the volume andrate of delivery according to the particular local physiologicalconditions encountered. The application of low pressure (i.e., nogreater than 360 psi), which is uniformly applied by the syringe 104 andthe tamping instrument 108, allows the physician to respond to fillvolume and flow resistance conditions in a virtually instantaneousfashion. The chance of overfilling and leakage of material 170 outsidethe cavity is significantly reduced.

When the physician is satisfied that the material 170 has been amplydistributed inside the cavity 168, the physician withdraws the tampinginstrument 108 from the cannula instrument 30. The physician preferablyfirst twists the tamping instrument 108 to cleanly break contact withthe material 170. The handle 60 can now be removed and the cannulainstrument 30 withdrawn, as FIG. 32 shows. The incision site is suturedclosed. The bone treatment procedure is concluded.

Eventually the material 170, if cement, will harden a rigid state withinthe cavity 168. The capability of the vertebral body 148 to withstandloads is thereby improved.

The selected material 170 can be an autograft or allograft bone grafttissue collected in conventional ways. For example, the graft materialcan be in paste form, as described by Dick, AUse of the AcetabularReamer to Harvest Autogenic Bone Graft Material: A Simple Method forProducing Bone Paste,@ Archives of Orthopaedic and Traumatic Surgery(1986), 105: 235-238, or in pellet form, as described by Bhan et al,APercutaneous Bone Grafting for Nonunion and Delayed Union of Fracturesof the Tibial Shaft, International Orthopaedics (SICOT) (1993) 17:310-312, both of which are incorporated herein by reference.Alternatively, the bone graft tissue can be obtained using a Bone GraftHarvester, which is commercially available from SpineTech. Using afunnel, the paste or pellet graft tissue material is loaded into thecannula instrument 30. The tamping instrument 108 is then advanced intothe cannula instrument 30 in the manner previously described, todisplace the paste or pellet graft tissue material out of the cannulainstrument 30 and into the cavity.

The selected material 170 can also comprise a granular bone materialharvested from coral, e.g., ProOsteonJ calcium carbonate granules,available from Interpore. The granules are loaded into the cannulainstrument 30 using a funnel and advanced into the cavity using thetamping instrument 108.

The selected material 170 can also comprise demineralized bone matrixsuspended in glycerol (e.g., GraftonJ allograft material available fromOsteotech), or SRSJ calcium phosphate cement available from Novian.These viscous materials, like the bone cement previously described, canbe loaded into the syringe 104 and injected into the cavity using thenozzle 106, which is inserted through the cannula instrument 30 into thecavity. The tamping instrument 108 is used to displace residual materialfrom the cannula instrument 30 into the cavity, as before described.

The selected material 170 can also be in sheet form, e.g. CollagraftJmaterial made from calcium carbonate powder and collagen from bovinebone. The sheet can be rolled into a tube and loaded by hand into thecannula instrument 30. The tamping instrument 108 is then advancedthrough the cannula instrument, to push and compact the material in thecavity.

VI. Alternative Embodiments

The use of low pressure delivery of material 170 frees the system 10from the need to accommodate relatively large diameter, high pressuredelivery devices. The interior diameter of the cannula instrument 30 canbe downsized accordingly, thereby minimizing the dimensions of thesubcutaneous pathway to gain access to the targeted bone region.

Typically, when low pressure material injection instruments are used,the largest tool that the reduced-diameter cannula instrument mustaccommodate is the expandable cavity-forming structure 82. The structure82 presents a minimal profile during deployment, as it can be collapsedand, if desired, a lubricous coating may also be applied to the exteriorof the structure 82 to facilitate its passage through thereduced-diameter cannula instrument.

A. Low Pressure Material Injection Instruments

FIG. 33 exemplifies low pressure material injection instruments 180 and182 that function in association with a cannula instrument 184 having areduced interior diameter, e.g. only about 3.4 mm or less.

One instrument 180 comprises a reduced-diameter nozzle. As FIG. 33shows, the nozzle 180 is sized to pass through the reduced-diametercannula instrument 184, to thereby pass into bone in the mannerpreviously shown in FIG. 26. The reduced-diameter nozzle 180 connects bya threaded connector 186 to the syringe 104. For material strength,despite its reduced dimension, the nozzle 180 is preferably formed froma rigid metal material, e.g., stainless steel.

As FIG. 33 shows, the reduced-diameter nozzle 180 also includes measuredmarkings 188 along its length, as previously described. The markings 188include a set point 190, as previously described, which aligns with theproximal end of the cannula instrument 184 when the distal ends of thecannula instrument 184 and the nozzle 180 align.

The other reduced diameter instrument 182 comprises a stylet, which issized to pass through the interior bore of the nozzle 180. The stylet182 includes a handle 192, which rests on the proximal connector 186 ofthe nozzle 180 when the stylet 182 is fully inserted into the nozzle180. When the handle 192 is rested, the distal ends of the stylet 182and nozzle 180 align. The presence of the stylet 182 inside the nozzle180 closes the interior nozzle bore.

In use, the nozzle 180 is coupled to the syringe 104 and insertedthrough the cannula instrument 184 into the material-receiving cavity168 formed in cancellous bone, in the same manner shown in FIG. 26.Material in the syringe 104 is injected at low pressure through thenozzle 180 into the cavity 168. As before explained, as the cavity 168progressively fills with material, the nozzle 180 is withdrawn back intothe cannula instrument 184. Typically, when the injection of material iscompleted, material extends from the cavity 168 and occupies about 40%to 50% of the cannula instrument 184.

At this point, the nozzle 180 can be fully withdrawn from the cannulainstrument 184 and unthreaded from the syringe 104. The stylet 182 canbe advanced into the nozzle 180, to bring the handle 192 at rest againstthe connector 186, thereby clearing residual material from the nozzle180. The nozzle 180 and stylet can then be inserted as a nested unitinto the cannula instrument 184. Nested together, the nozzle 180 andstylet 182 form a tamping instrument. Upon advancement through thecannula instrument 184, the nested nozzle 180 and stylet 182 displaceresidual material from the cannula instrument 184 into the cavity 168,in generally the same manner as previously shown in FIGS. 30 and 31,thereby uniformly compacting material within the cavity 168 in acontrolled fashion and without undue pressure.

Alternatively, a single-piece tamping instrument, separate from thenozzle 180, can be provided, downsized to fit through thereduced-diameter cannula instrument 184. In this embodiment, the stylet182 is not necessary, unless it is desired to reclaim material from thenozzle.

B. Cavity Forming Instrument

FIG. 34 shows a cavity forming instrument 194 intended to be deployedthrough the reduced-diameter cannula instrument 184, shown in FIG. 33.In many respects, the instrument 194 is like the instrument 76,previously described and shown in FIG. 4A, and common reference numeralswill be assigned to common structural elements. The instrument 184includes a flexible catheter tube 78 having a proximal end 80 and adistal end 82. The proximal end 80 carries a handle grip 84, and thedistal end 82 carries an expandable structure 86, which, when deployedin bone, compacts cancellous bone and forms the cavity 168.

Unlike the previously-described instrument 76, the instrument 194carries an introducer sleeve 196. The introducer sleeve 196 slides alongthe catheter tube 78 between the handle grip 84 and the expandablestructure 86. The introducer sleeve 196 includes a tubular main body 198with a forward collar 200 and a rear collar 202.

The introducer sleeve 196 normally occupies an advanced position on theinstrument 194, as shown in FIG. 35. In this position, the main body 198overlies and surrounds the expandable structure 86. The main body 198 issized to compress the structure 86 to an outside diameter that isslightly less than the interior diameter of the reduced-diameter cannulainstrument 184.

As FIG. 35 shows, when the introducer sleeve 196 occupies the advancedposition, the forward collar 200 extends beyond the distal end of thecompressed expandable structure 82. As FIG. 36 shows, in this position,the forward collar 200 presents itself for engagement with the proximalend 204 of the cannula instrument 184. The forward collar 200 is sizedto have an interior diameter that makes friction-fit engagement aboutthe proximal end 204 of the cannula instrument 184.

As FIG. 36 shows, when it is time to deploy the expandable structure 86through the cannula instrument 184, the physician engages the forwardcollar 200 of the introducer sleeve 196 in a friction fit about theproximal end 204 of the cannula instrument 184. As FIG. 37 shows,advancing the catheter tube 78 moves the compressed structure 86 throughthe main body 198 of the sleeve 196 and into the bore of the cannulainstrument 184. The engagement of the forward collar 200 about theproximal cannula end 204 aligns the axis of the structure 86 with theaxis of the cannula instrument 184, while compressing the structure 86to a diameter smaller than the interior of the cannula instrument 184.Upon advancement of the catheter tube 78, the introducer sleeve 196guides the structure 86 into the cannula instrument 194 without tearingor other damage.

Once the expandable structure 86 is advanced through the cannulainstrument 184 and into bone, the physician can slide the introducersleeve 196 rearward away from the proximal cannula end 204, to break thefriction fit between the end 204 and the forward sleeve. As FIG. 34shows, the rear collar 202 of the sleeve 196 is sized to make a snap fitengagement about a stem 206, which surrounds the catheter tube 78 nearthe handle 84. The snap fit engagement stabilizes the position of thesleeve 196 during subsequent use and manipulation of the cavity-forminginstrument 194.

The features of the invention are set forth in the following claims.

1-14. (canceled)
 15. A method comprising deploying a cannula throughsoft tissue to establish a subcutaneous path into bone, deploying acavity forming instrument through the cannula to form a cavity incancellous bone, inserting a nozzle into the cannula; and introducing amaterial into the cavity through the nozzle.
 16. The method of claim 15,wherein inserting the nozzle into the cannula comprises inserting adistal end of the nozzle into the cavity.
 17. The method of claim 16,wherein introducing includes delivering material at a pressure nogreater than about 360 psi.
 18. The method of claim 16, whereinintroducing includes using a manual syringe.
 19. The method of claim 16wherein the material comprises bone cement.
 20. The method of claim 16wherein the material comprises autograft tissue.
 21. The method of claim16 wherein the material comprises allograft tissue.
 22. The method ofclaim 16 wherein the material comprises synthetic bone substitute. 23.The method of claim 16 wherein the material comprises medication. 24.The method of claim 16 wherein the material comprises a material thatsets to a hardened condition.
 25. The method of claim 15 wherein thecavity forming instrument includes an expandable body, and whereindeploying the cavity forming instrument includes expanding theexpandable body to form the cavity.
 26. The method of claim 25 whereinexpanding the expandable body compresses cancellous bone.
 27. The methodof claim 25 wherein expanding the expandable body moves fracturedcortical bone.
 28. The method of claim 25 wherein the expandable bodyexpands by inflation.
 29. The method of claim 25 wherein the expandablebody includes a balloon.
 30. The method of claim 25, wherein deployingthe cavity forming instrument further includes: placing an elongateinstrument through the cannula to form a passage in the cancellous bone;and positioning the expandable body in the passage prior to expandingthe expandable body.
 31. The method of claim 30, wherein the elongateinstrument comprises an obturator.
 32. The method of claim 30, whereinthe elongate instrument comprises a drill.